Simple Interest Calculator: Interest and Maturity Amount

Simple interest is one of the easiest ways to estimate interest because the interest is calculated only on the original principal. It is useful for quick checks on short-term loans, deposits, advances, and fixed-rate arrangements where interest is not reinvested.

Use the Simple Interest Calculator to enter the principal amount, annual interest rate, and duration. The calculator shows the interest amount, maturity amount, and a monthly interest equivalent.

Simple interest formula

The basic formula is:

Simple interest = Principal x Rate x Time

Where:

• Principal is the original amount
• Rate is the annual interest rate divided by 100
• Time is the duration in years

Maturity amount is calculated as:

Maturity amount = Principal + Simple interest

For example, if the principal is Rs 1,00,000, the annual interest rate is 10%, and the duration is 3 years:

• Simple interest = 1,00,000 x 10% x 3
• Simple interest = Rs 30,000
• Maturity amount = Rs 1,30,000

When simple interest is useful

Simple interest is best when the agreement clearly says interest is calculated on the original amount only. It can be useful for:

• Short-term personal lending estimates
• Basic deposit or advance calculations
• Quick interest checks before reading detailed product terms
• Comparing a non-compounding option with a compounding option

If interest is added back to the principal and earns more interest, use the Compounding Calculator instead.

Simple interest vs compound interest

Simple interest does not earn interest on previous interest. Compound interest does. That is why compound interest can grow faster over longer periods.

For one-time investments where returns are reinvested, the Lumpsum Calculator may be a better estimate than a simple interest calculator.

Assumptions

• Interest is calculated only on the original principal.
• The annual interest rate remains fixed for the full duration.
• Duration is entered in years.
• Taxes, fees, penalties, prepayments, and compounding are not included.

Disclaimer

The information and calculations provided on this website are for general informational and educational purposes only. Results are estimates based on user inputs and assumptions and may not reflect actual financial outcomes. This content does not constitute tax, legal, accounting, or financial advice. Consult a qualified professional before making financial decisions.